Dynamic cache partitioning for shared Last Level Caches (LLC) is deployed in most modern multicore systems to achieve process isolation and fairness among the applications and avoid security threats. Since LLC has visibility of all cache blocks requested by several applications running on a multicore system, a malicious application can potentially threaten the system that can leverage the dynamic partitioning schemes applied to the LLCs by creating a timing-based covert channel attack. We call it as Cache Partitioned Covert Channel (CPCC) attack. The malicious applications may contain a trojan and a spy and use the underlying shared memory to create the attack. Through this attack, secret pieces of information like encryption keys or any secret information can be transmitted between the intended parties. We have observed that CPCC can target single or multiple cache sets to achieve a higher transmission rate with a maximum error rate of 5% only. The paper also addresses a few defense strategies that can avoid such cache partitioning based covert channel attacks. © 2021 EDAA.